The present invention relates generally to disc brakes and, more particularly, to a braking caliper for a pressure-medium-operated spot-type disc brake comprising at least one wheel cylinder held in the braking caliper, including a piston for forcing the brake pads into contact with the brake disc enclosed by the brake caliper.
One known type of spot-type disc brake is shown in U.S. Pat. No. 3,548,973. The disc brake is equipped with a separately formed wheel cylinder the housing of which, on two oppositely arranged sides, comprises strip-type projections disposed in parallel with respect to one another by way of which the wheel cylinder is held in corresponding grooves cut into the braking caliper. A spring-loaded bolt or locking bar is provided for preventing the wheel cylinder with the two strip-type projections thereof from inadvertently slipping from the grooves of the braking caliper. Such a conventional spot-type disc brake has the disadvantage that forming the grooves in the braking caliper requires a labor and cost-intensive machining method. Further, the strip-type projections require machining of at least two respective side faces resulting in a further cost increase. The state-of-the-art braking caliper involved the risk of being overloaded in the area of the grooves causing the same to break out; however, a braking caliper specifically reinforced at the endangered points is of a relatively heavy weight and a large structural volume increasing for example, the mass on the wheel of the motor vehicle.
A another conventional spot-type disc brake in shown in U.S. Pat. No. 3,734,243. The disc brake shown in that patent has a separate pot-shaped wheel cylinder which includes a circumferential collar engaging a U-shaped recess provided in one of the cheeks of the braking caliper. Such engagement prevents the wheel cylinder from displacing toward the longitudinal axis of the wheel cylinder bore. The pot-shaped wheel cylinder is inserted into the corresponding U-shaped recess in the radial direction, i.e. crosswise of the longitudinal axis of the wheel cylinder and from the bottom into the braking caliper. The cylinder is locked with the aid of a spring-loaded locking bolt to prevent inadvertent slipping out. For this purpose, the wheel cylinder includes a radially extending ear-shaped lug which is provided with a bore engaging the locking bolt disposed in the braking caliper when the wheel cylinder has turned into its operating position. Such prior art spot-type disc brake has the disadvantage that the U-shaped recess in the caliper is difficult to manufacture. Moreover, the wheel cylinder is safely supported only on a part of the collar by a positive connection. Accordingly, the braking caliper is required to have comparatively strong walls in the area of the U-shaped recess. Finally, locking by use of a locking bolt in a bore in the braking caliper and a spring is both unreliable and costly.
Accordingly, it is an object of the present invention to provide an improved spot-type disc brake.